This invention relates generally to gravel packing of oil, gas, or water wells, and particularly to a method and apparatus for such gravel packing utilizing a perforate liner, a wash pipe within the liner, and a cross-over tool connected to the wash pipe having a pair of reversible fluid passages therein.
As an example of prior art apparatus, reference is made to U.S. Pat. No. 3,421,586 dated Jan. 14, 1969, and entitled "Flow-Reversing Liner Shoe for Well Gravel Packing Apparatus". This reference shows apparatus for gravel packing a perforate liner in a well including a cross-over tool supported from well tubing, and a wash pipe connected to the cross-over tool and received in concentric relation within the perforate liner. In operation, during the wash-down procedure in which sand is carried upwardly in the annular space between the exterior of the liner and the interior of the casing, the flow is directed downwardly to open the back flow check valve thereby to provide a jet action to stir up the sand for removal until the liner and associated structure is positioned at the desired depth in the well for gravel packing. Fluid flow in an upward direction in the inner annulus at the lower end of the wash pipe inside the liner is prevented by the bypass means shown in FIG. 4 of aforesaid U.S. Pat. No. 3,421,586 during the wash-down procedure. With the liner positioned at the desired depth the direction of fluid flow in the wash pipe is reversed and gravel packing commences by the pumping of fluid with entrained gravel down through the tubing and then out into the outer annulus outside the liner. However, upon a reversal of fluid flow in the wash pipe to an upward direction for the gravel pack step, fluid flow is permitted downwardly in the annulus about the wash pipe by the bypass means. Such a bypass means acts as a restriction on the downward fluid flow in the annulus within the liner during the gravel pack procedure, and may be undesirably held in a partially open position by foreign matter such as sand or gravel during the initial wash-down procedure. After the gravel has been packed to a predetermined height about the liner, the releasing tool, pack-off tool, and wash pipe are removed from the liner and lifted upwardly with a continued fluid circulation to clean out any fine particles remaining in the liner after the gravel packing. Then, the tubing is lifted for removal of the cross-over tool, releasing tool, and the wash pipe from the well leaving the liner in position for completion of the well for production.
Reference is also made to U.S. Pat. No. 3,913,676 dated Oct. 21, 1975, entitled "Method and Apparatus for Gravel Packing" which shows a method and apparatus for gravel packing a well utilizing cross-over equipment having a production screen. This reference during the wash-down step as shown in FIG. 1B has seals about the lower end of the wash pipe so that the downward flow of flushing fluid in the wash pipe opens the discharge valve and produces a jet action adjacent the end of the liner. After the wash-down step and before the gravel pack procedure, a ball is pumped down the wash pipe or tubing and fluid pressure then moves an inner sleeve downwardly to expose parts so that fluid may flow downwardly in the annular inside the liner and up the wash pipe during the gravel pack procedure. Thus, an additional intermediate step is required between the wash-down procedure and the gravel pack procedure or step.
The above references are examples of prior art apparatus which have been utilized heretofore in gravel packing apparatus in which a sealing connection is required between the lower portion of the work pipe and the liner during the initial wash-down phase with the fluid flow down the wash pipe to prevent an upward fluid flow in the annulus between the liner and wash pipe and a resulting dissipation of fluid pressure from the end of the wash pipe. During the gravel packing step in which the fluid flow is up the wash pipe, it is necessary that this sealing connection be broken so that fluid may flow down the annulus in the liner adjacent the lower portion of the wash pipe. These references accomplish gravel packing without any raising or lifting of the tubing or other supporting apparatus from the ground surface, except upon final disassembly from the liner, but they do require additional steps or additional structures.
A further example of an apparatus and a method for gravel packing a well is shown in U.S. Pat. No. 4,018,284 dated Apr. 19, 1977, and entitled "Apparatus and Method for Gravel Packing a Well" which utilizes a hydraulically actuated fluid diverting means for passageways in the apparatus.